[hansvm]

> global to your whole program

Zig automatically does what most languages call LTO, so "whole program" and "compilation unit" are effectively the same thing (these error indices don't propagate across, e.g., dynamically linked libraries). If you have a bunch of ZIg code calling other Zig code and using error types, they'll all resolve to the same global error type (and calling different code would likely result in a different global error type).

> distinct error type, why?

The langage is very against various kinds of hidden "magic." If you take for granted that (1) error paths should have language support for being easily written correctly, and (2) userspace shouldn't be able to do too many shenanigans with control flow, then a design that makes errors special is a reasonable result.

It also adds some homogeneity to the code you read. I don't have to go read how _your_ `Result` type works just to use it correctly in an async context.

The obvious downside is that your use case might not map well to the language's blessed error type. In that case, you just make a normal record type to carry the information you want.